Searching is an iterative process. You may find yourself adding and removing subject headings, keywords and limits as you continuously refine your search strategy. Explore the different components of a search strategy using the tabs below.
A gold set is a set of seed articles which are highly relevant to your question and will be included in your literature/systematic review results.
Subject headings are "controlled vocabulary" that are used by databases to ensure that items relevant to a particular topic can be found. This means that you will need to know and use the right term to describe your key concept. Subject headings ensure that the same terminology is used to describe each concept and are similar in function to tags.
Not all databases use the same type of headings so check before you use them in your search.
The table below shows the subject headings used by databases available from the library.
| Subject Headings | Databases | Example Term | Subject Heading Used |
| Medical Subject Headings (MeSH) | Medline, Pubmed, Cochrane Library | Heart attack | Myocardial Infarction |
| Emtree Subject Headings | Embase, Emcare | Heart attack | Heart Disorders |
| APA Thesaurus of Psychological Index Terms | APA PsycInfo | Heart attack | Heart Infarction |
| CINAHL Subject Headings | CINAHL | Heart attack | Myocardial Infarction |
Where can I find the subject headings?
You can search for MeSH within PubMed or Ovid Medline. MeSH are also publicly available via the MeSH Browser.
As for Emtree, APA Thesaurus of Psychological Index Terms and CINAHL Subject Headings, they are only searchable within the appropriate databases.
There are a few ways to ensure you have selected the most appropriate subject headings in your search strategy:
Subject headings in PubMed
PubMed uses automatic term mapping. This means that when you put a word in the search box, PubMed automatically maps your word to MeSH and keyword fields. In other databases, you have to input subject headings and keywords separately and manually. To check that your MeSH has been correctly mapped, click the 'Advanced' link under the search box and scroll down to 'History and Search Details'.
In the example below, a search was done using the term 'dermatitis'. PubMed has mapped this term to the MeSH term 'dermatitis' and also searched for the keyword 'dermatitis' in all fields.
When using subject headings, you will notice that there are options to explode, focus or use subheadings. Each database uses different terms to describe these functions. Explore them using the buttons below.
What does 'explode' mean?
When the 'explode' function is selected for a subject heading, the subject heading and all other narrower terms below it are selected and searched by the database. It is a quick and easy way to select multiple related subject headings all at once.
Ovid Medline
When the MeSH term Dermatitis is selected and exploded, all other MeSH terms below Dermatitis (and including Dermatitis itself) will be included in your search. The exploded MeSH term will be presented as: exp Dermatitis/.
If you only wanted a few MeSH terms e.g. Dermatitis, Dermatitis, Atopic and Eczema in your search, you would select these MeSH terms individually without exploding Dermatitis itself.
Other Ovid databases (Embase, Emcare, PsycInfo)
The explode function works in the same way as Ovid Medline, although the subject headings may be different.
PubMed
In PubMed, each MeSH term is automatically exploded. This means that "Dermatitis"[MeSH Terms] also automatically includes "Acrodermatitis"[MeSH Terms], "Dandruff"[MeSH Terms], "Dermatitis, Atopic"[MeSH Terms]... and so on.
To find out what terms have been included, you can do a search on the MeSH Browser to see the MeSH Tree Structures.
You can select whether you want the MeSH term to be exploded by going to PubMed and clicking on MeSH Database (under Explore) on the front page, or follow the link provided.
Do a search for your subject heading, e.g. Dermatitis and click on the MeSH term. Tick the 'Do not include MeSH terms found below this term in the MeSH hierarchy' box and click the 'Add to search builder' button under the search box on the right side of the page.
The MeSH term will be presented as: "Dermatitis"[Mesh:NoExp].
CINAHL
When the CINAHL subject heading Dermatitis is selected and exploded, all other subject headings below Dermatitis (and including Dermatitis itself) will be included in your search. The exploded subject heading will be presented as: MH "Dermatitis+".
If you only wanted Dermatitis, Dermatitis, Atopic and Eczema in your search, you would select these subject headings individually without exploding Dermatitis itself.
Cochrane Library
In Cochrane Library, you can see where Dermatitis sits in the hierarchy and explode all trees (if there are more than one tree) or explode selected trees only. In this example, there is only one tree to be exploded, so Dermatitis and all the MeSH terms below it will be selected and searched.
The exploded subject heading will be presented as: MeSH descriptor: [Dermatitis] explode all trees.
Using Eczema as an example, if there were one or more trees that could be selected and only one was selected, the exploded subject heading will be presented as: MeSH descriptor: [Eczema] 1 tree(s) exploded.
What does 'focus' mean?
Some articles have a main theme or focus on a particular topic and they are tagged with a 'focus' subject heading. To find these articles, you would select a subject heading and use the 'focus' function. Note that if you do not focus the subject heading, the subject heading will retrieve all items tagged with the subject heading – regardless of whether the item has a focus on the topic or not.
Important note: Focus is a powerful function that can help you find relevant items quickly. However, this function is generally not recommended for literature and systematic searching as you may accidentally omit relevant items in the process. Try using subheadings (see the section on subheadings below) instead so you have more control over your search.
Ovid Medline
When the focus function for the MeSH term has been selected, the MeSH term will be presented as: *Dermatitis/.
Other Ovid databases (Embase, Emtree, PsycInfo)
The focus function works in the same way as Ovid Medline, although the subject headings may be different.
PubMed
In PubMed, the focus function is called Major Topic. You can select whether you want the MeSH term to be focused by going to PubMed and clicking on MeSH Database (under Explore) on the front page, or follow the link provided.
Do a search for your MeSH term, e.g. Dermatitis and click on the subject heading. Tick the 'Restrict to MeSH Major Topic' box and click the 'Add to search builder' button under the search box on the right side of the page.
The MeSH term will be presented as: "Dermatitis"[Majr].
CINAHL
In CINAHL, the focus function is called Major Concept. When Major Concept is selected, the CINAHL subject heading will be presented as: MM "Dermatitis+".
Cochrane Library
The focus function is not available in Cochrane Library.
What are subheadings?
Subheadings are subdivisions of subject headings. The use of subheadings in your search strategy to narrow down the number of results is highly recommended. Select as many subheadings as you like in your search. If none are selected then all subheadings are included by default.
Subheadings can be used together with either the explode, focus or both functions at the same time.
Ovid Medline
If the diagnosis subheading is selected, the Dermatitis MeSH term will be presented as: Dermatitis/di [Diagnosis].
If more subheadings are selected, the Dermatitis MeSH term will be presented as: Dermatitis/ep, ge, pp [Epidemiology, Genetics, Physiopathology].
Other Ovid databases (Embase, Emtree, PsycInfo)
The subheadings function works in the same way as Ovid Medline, although the subheadings may be different.
PubMed
You can select subheadings by going to PubMed and clicking on MeSH Database (under Explore) on the front page, or follow the link provided.
Do a search for your subject heading, e.g. Dermatitis and click on the subject heading. Then tick the subheadings you want and click the 'Add to search builder' button under the search box on the right side of the page.
The MeSH term will be presented as: "Dermatitis/diagnosis"[Mesh].
If multiple subheadings are selected, the MeSH term will be presented as: ("Dermatitis/epidemiology"[Mesh] OR "Dermatitis/genetics"[Mesh] OR "Dermatitis/physiopathology"[Mesh]).
CINAHL
When the box for the CINAHL subject heading is ticked, a list of subheadings will appear.
If only one subheading is selected, the CINAHL subject heading will be presented as: MH "Dermatitis/DI".
If multiple subheadings are selected, the CINAHL subject heading will be presented as: MH "Dermatitis/EP/PP".
Cochrane Library
Search for the subheading you want by using the box provided.
If only one subheading is selected, the MeSH term will be presented as: MeSH descriptor: [Dermatitis] this term only and with qualifier(s): [diagnosis - DI].
If multiple subheadings are selected, the MeSH term will be presented as: MeSH descriptor: [Dermatitis] this term only and with qualifier(s): [genetics - GE, epidemiology - EP, physiopathology - PP].
Keywords are natural language terms used to describe your key concepts. The terms used can be varied, so try to think of the different terms that authors might use to describe a key concept. Some examples are shown in the table below.
| Acronyms | electrocardiogram or ECG |
| Alternate spellings |
fetus or foetus child care or childcare speech language pathologist or speech-language pathologist |
| Plural forms |
child or children woman or women man or men |
| Shortened words | caesarean or C-section |
| Synonyms | lumbar puncture or spinal tap |
| Word variations | standard or standards or standardised (or standardized) or standardisation (or standardization) |
Where can I find keywords?
There are a few ways to ensure you have included all relevant keywords in your search strategy:
Remember – To search effectively in databases, you should use a combination of subject headings and keywords.
Boolean operators (AND / OR) are used to combine multiple search concepts.
AND is used to search for items that contain both terms, e.g. ear infection AND antibiotics. Generally used to combine different concepts.
OR is used to broaden your search by finding any results that contain either one of your terms, e.g. lumbar puncture OR spinal tap. Generally used to include synonyms of the same concept.
Use parentheses to group concepts in your search, e.g. (otitis media OR ear infection) AND (anti-bacterial agents OR antibiotics)
Database search functionality is similar across all databases. However, each database understands and presents search operators or syntax differently. Use the help function in the database when you are unsure.
Ovid field codes
When searching in Ovid databases (Medline, Embase, Emcare, PsycInfo), you can search keywords in different fields. Here are some of the commonly used field codes:
Stands for multi-purpose. Default keyword field code for Ovid, which searches all fields. E.g. antibiotics.mp.
Stands for title. Searches the article title field. E.g. antibiotics.ti.
Stands for abstract. Searches the article abstract field. E.g. antibiotics.ab.
Stands for keyword heading word. Searches all author keyword headings that contains a particular word. Search using a single word in this field. E.g. antibiotics.kf.
Tip 1: You can combine field codes by using a comma, e.g.. This allows you to search in both the title and abstract of the article at the same time, e.g. antibiotics.ti,ab.
Click the button below to see the full list of Ovid Field Codes.
Search operators/syntax
| Truncation | Optional Wildcard | Mandated Wildcard | Phrase Search | Proximity | |
| Used For | Searching variations of the word, e.g. palliate, palliates, palliation, palliative etc. | Searching spelling variations of zero or one character, e.g. fetus/foetus, service/services | Searching spelling variations of exactly one character, e.g. woman/women. | Searching keywords in the exact order. | Searching keywords in any word order, e.g. rehabilitative model or models for rehabilitation. |
|
Ovid databases |
Use an asterix (*). Example: |
Use a question mark (?). Example: |
Use a hash symbol (#). Example: |
No quotation marks required. Example: |
Use adjn, where n is the maximum number of words apart. Example: |
|
PubMed (Note: The use of any of these search operators turns off PubMed's automatic term mapping feature.) |
Use an asterix (*). Example: |
Not supported | Not supported |
Use double quotation marks. Example: |
Use "search terms"[field:~n], where n is the maximum number of words apart. Example: Note: Proximity searching can only be used in the Title or Title/Abstract fields. Terms cannot be truncated when using proximity searching, e.g. you will get an error if you search "rehabilitation model*"[Title/Abstract:~2] (note the asterix at the end of the word 'model') To search variations, spell the terms out exactly, e.g. ("rehabilitation model"[Title/Abstract:~2] OR "rehabilitation models"[Title/Abstract:~2]) |
| CINAHL |
Use an asterix (*). Example: |
Use a hash symbol (#). Example: |
Use a question mark (?). Example: |
Use double quotation marks. Example: |
Use Nn, where n is the maximum number of words apart. Example: |
| Cochrane Library |
Use an asterix (*). Example: |
Use a question mark (?). Example: |
Use a question mark (?). Example: |
Use double quotation marks. Example: |
Use NEAR/n, where n is the maximum number of words apart. Example: |
Tip 2: When using truncations and wildcards, think about the word variations that may be used by authors. However, be aware of what your truncated words are retrieving, e.g. trans* could mean transgender or transplant.
Tip 3: When using the adjacency search operator, think of how far apart commonly used phrases are.
Depending on your requirements, you can add limits to your search such as age groups, year of publication, language, types of publication and more.
Adding limits
Click the buttons below to see how to add limits in each database.
Ovid databases (Medline, Embase, Emcare, PsycInfo)
PubMed
button to limit the search results by Article Type, Article Language, Age and more.
CINAHL
Cochrane
button to limit your search results by publication date.
Using pre-built search filters
Pre-built search filters are validated searches created by information experts and have undergone tests to ensure the retrieval papers that are of high quality and relevant to the specific search.
You can incorporate these pre-built search filters in your own search strategy.
A sensitive search is a broader search that aims to retrieve all relevant results.
Pros: There is little risk of omitting relevant results.
Cons: You will have a larger number of results to screen/read through.
A specific search is a narrower search that aims to retrieve only the most relevant results.
Pros: You will have a smaller number of results to screen/read through.
Cons: There is a high risk of omitting some relevant results.
A balanced or optimised search is the middle ground between a sensitive and specific search.
In Ovid databases and CINAHL, you have the option of adding sensitivity and specificity filters to your search. Click on the buttons below to see how.
Ovid databases (Medline, Embase, Emcare, PsycInfo)
CINAHL
Patient scenario
Kate is 6 years old and suffers from middle ear infections often. After examination, you believe that Kate is suffering from acute otitis media and you prescribe a dose of oral antibiotics. Kate’s mother asks if the antibiotics are really necessary.
PICO
Patient/population - Children with acute otitis media
Intervention - Oral antibiotics
Comparison - No oral antibiotics
Outcome - Improvement in symptoms
Clinical question
Among children with acute otitis media, does treatment with oral antibiotics result in an improvement in symptoms as compared to no treatment?
Search strategy example
Below is an example of a basic search strategy which has been completed in Ovid Medline, with a limit of articles published in the last 5 years.
Once you are satisfied with your search in one database, run your search in another 2 or 3 databases to ensure that you have identified as many relevant articles as possible. To do this, you have to 'translate' your search from one database to another.
Click the buttons below to see the translated search in other databases.
Ovid Medline search strategy translated to Ovid Embase (this technique will also work for any Ovid databases):
Ovid Medline search strategy translated to CINAHL:
Ovid Medline search strategy translated to Cochrane Library (using Search Manager):
It is important to keep a record of your search as it helps you keep track of the subject headings and keywords you have included in your search strategy. It also allows you to share and reproduce the search if required.
Recording search terms
There is no prescribed method to record your search terms. A simple template and example is provided below. Compiling your search terms in this format allows you to keep track of the terms that you have included in your search.
| CONCEPT | KEYWORDS | MESH HEADINGS | EMTREE HEADINGS | CINAHL (if applicable) |
APA THESARUS OF PSYCHOLOGICAL INDEX TERMS (if applicable) |
| Ear Infection |
acute otitis media, |
Otitis Media | Otitis Media | ||
| Antibiotics | antibacterial, antibacterials, anti bacterial, anti bacterials, antibiotic, antiobiotics |
Anti-Bacterial Agents | Antibiotic Agent |
Recording your search process
You may also want to record your search progress as you begin your search, particularly for long-term projects. This document will be a reminder of where and how you located your search results.
You can make a note of:
Saving, sharing & exporting your search strategy & results
Saving and/or exporting your search results will allow you to run your search strategy again at a later date, and share your search results with others.
Databases will allow you to save and share your search strategy with syntax and field codes included and export your search results to commonly used formats such as Microsoft Word, Excel, PDF or RIS (for reference managers).
Visit our 'Saving, sharing & exporting your searches' page for more information.
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